A hot air dryer with a cylindrical housing is shown and described in U.S. Pat. No. 5,570,517 issued Nov. 5, 1996 the disclosure of which is incorporated herein by reference. That dryer has a cylindrical housing. A rotatable shaft extends through the housing. The housing has an inlet end for admitting material to be dried and hot air to dry it. The inlet end of the shaft carries disks that carry scraper blades. The scraper blades are mounted to scrape the inside wall of the housing. The last upstream disk carries end wall scraper blades that scrape the inlet end wall of the housing. The scraper blades prevent material that enters the housing from adhering and remaining on the side and end wall of the housing. The remainder of the shaft carries retention paddles. Shaft mounted and wall mounted air dams are located along the length of the housing. A discharge opening is at the outlet end of the housing for discharge of material that is drier than it was when it entered the inlet end.
The end wall scrapers are necessitated by the location of the material inlet at the end wall of the housing. Material tends to collect on the end wall and must be removed. Elimination of these end wall and side wall scrapers is desirable in terms of simplifying the structure and reducing maintenance requirements.
In addition, material tends to accumulate between the disks. This material will eventually dry and, in some instances, burn. Elimination of this accumulation region is desirable.
The invention pertains to an improved hot air material or slurry dryer of the type discussed above but wherein a product inlet is connected to the side of the cylindrical housing as opposed to the end wall. The end wall is no longer a problem in terms of the formation of a build-up of material that needs to be removed. In one preferred embodiment a drum is mounted toward the upstream end of the shaft. The drum carries a plurality of agitator blades to agitate the incoming material to dry it. The agitator blades can be arranged in a spiral pattern about the drum in order to influence downstream movement of subject material. Retention paddles can be mounted along the remainder of the shaft.